1. Field of the Invention
The present invention relates to a durable endless metal belt for a metal belt type nonstep variable-speed transmission.
2. Description of the Related Art
When a metal belt type nonstep variable-speed transmission including a drive pulley, a driven pulley and an endless metal belt formed by engaging blocks with a layered ring formed by radially superposing thin metal rings, and extended between the drive and the driven pulley is in operation, the metal blocks are tilted about an axis perpendicular to a plane in which the endless metal belt turns due to the lateral dislocation of the endless metal belt and the inner side edges of the thin metal rings are pressed strongly against the side edges of neck parts of the metal blocks, so that the inner side edges of the thin metal rings are subject to damaging.
A technique proposed in JP-U No. Sho 63-82842 (JP-U No. Hei 5-8358) to prevent such a problem rounds each of the side surfaces of a neck part of the metal block in a curved surface of a predetermined radius of curvature about the front and the rear edge of the opposite side surfaces of the metal block, and rounds the intersection of the curved surfaces in a predetermined radius of curvature.
An invention disclosed in JP-A No. Hei 2-146334 rounds the side edges of a neck part of a metal block in a curved edge of 0.2 m in radius of curvature. However, neither of the prior art techniques determines the shape of the side edges of the neck part of the metal block rationally on the basis of the relation between a stress induced by a local pressure applied to the inner side surface of the thin metal ring and another stress induced in the thin metal ring.
In the aforesaid prior art, the curved side edge of the neck part of the metal block has a big radius of curvature, the side edge of the neck part of the metal block, which is difficult to machine, must be cut greatly, troublesome work is necessary for the inspection of the side edge of the neck part of the metal block to see if the side edge is rounded in a predetermined radius of curvature, the processing and inspection of the metal block takes much time and the metal block is produced at a low productivity.
It is an object of the present invention to incorporate improvements into such an endless metal belt for a metal belt type nonstep variable-speed transmission.
According to a first aspect of the present invention, an endless metal belt for a metal belt type nonstep variable-speed transmission, extended between a drive pulley and a driven pulley included in the metal belt type nonstep variable-speed transmission, the respective effective diameters of the drive and the driven pulley being variable to change speed change ratio, comprises: thin metal rings layered in thicknesses to form two layered ring structures; and a plurality of metal blocks arranged along and supported on the two layered ring structures; wherein the side edges of the inner and the outer circumference of each of the thin metal rings are rounded in round edges of a radius RR of curvature, middle parts of the opposite side surfaces of each thin metal ring are flat, front and rear edges of opposite side surfaces of a neck part of each metal block are rounded in round edges of a radius R0 of curvature, respectively, and the radius RR of curvature of the round side edges of the inner and the outer circumference of each thin metal ring and the radius R0 of curvature of the front and the rear round edge of opposite side surfaces of the neck part of each metal block are determined so that a stress relating to fatigue strength and induced in the inner circumference of the innermost thin metal ring is equal to or lower than a stress relating to fatigue strength and induced in the inner side surface of the thin metal ring by the front and the rear round edge of the side surface of the neck part of the metal block that comes into contact with the thin metal ring.
In the endless metal belt according to the first aspect of the present invention, damaging of the flat middle part of the inner side surface of the thin metal ring that touches the round edges of the side surface of the neck part of the metal block is avoided, the lest possible radius R0 of curvature of the round edges of the side surface of the metal block is selected in relation with the radius RR of curvature of the round edges of the opposite side surfaces of the thin metal ring to reduce the amount of machining in finishing the metal block, so that the metal block can be manufactured at a greatly improved productivity at a low cost.
According to a second aspect of the present invention, an endless metal belt for a metal belt type nonstep variable-speed transmission, extended between a drive pulley and a driven pulley included in the metal belt type nonstep variable-speed transmission, the respective effective diameters of the drive and the driven pulley being variable to change speed change ratio, comprises: thin metal rings layered in thicknesses to form two layered ring structures; and a plurality of metal blocks arranged along and supported on the two layered ring structures; wherein front and rear edges of opposite side surfaces of a neck part of each metal block are rounded in round edges of a radius R0 of curvature, the thin metal rings has a thickness t, and the radius R0 of curvature is not less than t/3.
In the endless metal belt according to the second aspect of the present invention, damaging of the flat middle part of the inner side surface of the thin metal ring can be avoided by properly determining the value of the radius R0 of curvature of the rounded front and rear edges of opposite side surfaces of the neck part of each metal block in relation with the thickness t of the thin metal ring.
According to a third aspect of the present invention, an endless metal belt for a metal belt type nonstep variable-speed transmission, extended between a drive pulley and a driven pulley included in the metal belt type nonstep variable-speed transmission, the respective effective diameters of the drive and the driven pulley being variable to change the speed ratio, comprises: thin metal rings layered in thicknesses to form two layered ring structures; and a plurality of metal blocks arranged along and supported on the two layered ring structures; wherein RR is in the range of 0.04t/0.18 to 0.07t/0.18 and R0xe2x89xa7t/3, where RR is the radius of curvature of the round side edges of the inner and the outer circumference of each of the thin metal rings, R0 is the radius of curvature of the front and the rear round edge of opposite side surfaces of a neck part of each metal block and t is the thickness of the thin metal rings, the radius R0 of curvature of the front and the rear round edge of opposite side surfaces of the neck part of each metal block is big when the radius RR of curvature of the round side edges of the inner and the outer circumference of each of the thin metal rings is big, and the radius R0 of curvature of the front and the rear round edge of opposite side surfaces of the neck part of each metal block is small when the radius RR of curvature of the round side edges of the inner and the outer circumference of each of the thin metal rings is small.
According to a fourth aspect of the present invention, an endless metal belt for a metal belt type nonstep variable-speed transmission, extended between a drive pulley and a driven pulley included in the metal belt type nonstep variable-speed transmission, the respective effective diameters of the drive and the driven pulley being variable to change speed change ratio, comprises: thin metal rings layered in thicknesses to form two layered ring structures; and a plurality of metal blocks arranged along and supported on the two layered ring structures; wherein the side edges of the inner and the outer circumference of each of the thin metal rings are rounded in round edges of a radius RR of curvature, middle parts of the opposite side surfaces of each thin metal ring are flat, front and rear edges of opposite side surfaces of a neck part of each metal block are rounded in round edges of a radius R0 of curvature, respectively, and the radius RR of curvature of the round side edges of the inner and the outer circumference of each thin metal ring and the radius R0 of curvature of the front and the rear round edge of opposite side surfaces of the neck part of each metal block meet the following inequality.
RRxe2x89xa635R03xe2x88x9212.7R02+1.59R0+0.01
Thus, the lest possible radius R0 of curvature of the round edges of the side surface of the metal block is selected in relation with the radius RR of curvature of the round edges of the opposite side surfaces of the thin metal ring to reduce the amount of machining in finishing the metal block, so that the metal block can be manufactured at a greatly improved productivity at a low cost.